1 PAEDIATRICS Neuromuscular Disorders Diploma of Paediatrics. Dr Rakesh Patel Neuromuscular Disorders Approach Localisation Investigations Examples Nerve NMJ Muscle Other Neuromuscular Disorders Approach Presenting History Presenting signs and symptoms Clinical patterns When considering a neuromuscular disease you should concentrate on the following . Functional disability. Anatomical distribution. Temporal relationship in time. Presenting History Functional disability Especially useful to help develop your differential diagnosis. Look for selective involvement in these systems. Motor Sensory Autonomic Presenting History Anatomical distribution Arms vs. Legs Most neuromuscular disorders are more prominent in the legs or involve both arms & legs.
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PAEDIATRICS
Neuromuscular Disorders
Diploma of Paediatrics.
Dr Rakesh Patel
Neuromuscular Disorders
ApproachLocalisationInvestigationsExamples
NerveNMJMuscleOther
Neuromuscular Disorders
Approach
Presenting History
Presenting signs and symptomsClinical patterns
When considering a neuromuscular disease you should concentrate on the following .
Functional disability.Anatomical distribution.Temporal relationship in time.
Presenting History
Functional disabilityEspecially useful to help develop your differential diagnosis.
Look for selective involvement in these systems.
MotorSensoryAutonomic
Presenting History
Anatomical distributionArms vs. Legs
Most neuromuscular disorders are more prominent in the legs
or involve both arms & legs.
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Presenting History
Anatomical distributionProximal vs. Distal
Myopathies have a distribution of weakness that is usually proximal.
Neuropathies, sensory loss and weakness is usually more distal then proximal.
Presenting History
Anatomical distributionSymmetric vs. Asymmetric
Symmetric disorders are more common.MyopathiesNeuropathies
Asymmetric weakness: Commonly treatableOften related to inflammatory disorders.Local pathology.
Presenting History
Temporal relationshipCoarse
Acute: Days to Weeks Chronic: Months to Years Episodic
Diurnal variationOnset age
Paediatric: Neonatal; Childhood Adult: 20 to 60 years; Geriatric
HereditaryBy family history or examination of relatives.
Presenting History
Past historyBirth historyDevelopmental historyPast medical history
Family historyPatterns of inheritance
The Examination
Full neurological examinationMotorSensoryCognitive
Note the features
Long faciesBitemperal wastingOpen mouth
High arched palette
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Gower’s manoeuver
Described first by Sir William Richard GowersDifficulty rising from the floor because of proximal weakness.
PsuedohypertrophyNote the bulky musclesMuscles are firm to palpationHowever the muscle is weak on strength testing.
Champaign bottle legsDistal wasting of musclePoor dorsiflexionPoor eversionOften associated pescavus
Pes cavus
Slowly deforming Poor dorsiflexionPoor eversionOften ending in a fixed deformity
Percussion myotonia
Slow flexion of the thumb after percussion of the thenar prominenceOccurs in myotonicsyndromes
Poor reflexes+/- cognitive involvementOther features
MyotoniaCardiomyopathyFacial involvement
Where is the lesion - Muscle
CongenitalMyopathyDystrophy
InflammatoryDermatomyositis
InfectiveMyositis
Metabolic
Investigations
RoutineSpecific
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Investigations
Always start with the basicsFBCElectrolytesCa, MgGlucoseLFT’sBlood gas statusCK
Why do a CK?
Dystrophy Relatively high CKdegenerative loss and destruction of a previously normal architecture
Myopathy minimal increase in CKabnormality in architecture,
Investigations
Neurophysiological
EMGNCS
Often help to determine if the pathology lies in the nerve, neuromuscular junction or muscle.
EMG
Motor unit examination
Denervation produces reduced number of motor unit action potentials.
Denervation produces fibrillations.
Neuropathy with reinnervation produces increased amplitude motor unit potential.
EMG
Motor unit examinationMyopathy produces decreased size of motor unit potential.Myotonia produces a distinctive ‘dive bomber’ response.Myasthenia produces a decrementalresponse.
NCS
Demyelinationproduces slowed nerve conduction.
Axonal degenerationproduces decreased amplitude of nerve action potential.
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NCS
Proximal conduction block occurs in Guillain-Barre.
Abnormal F-wave (absent) and abnormal F-wave ratio (increased).
Investigations
Biopsy
MuscleNerve
Often helps to determine what the pathological process is affecting the muscle or nerve.
Western blot of dystrophin from dystrophinopathies.1: Becker dystrophy; Dystrophin has reduced abundance but normal size.2: Becker dystrophy; Dystrophin has reduced size and abundance.3: Normal; Dystrophin has normal size and amount.4: Duchenne dystrophy; Almost no protein is present.5: Duchenne outlier; Dystrophin has severely reduced abundance.
Nerve biopsy
Histology
EM
Nerve biopsy
Demylination
Normally myelinated motor axon in muscle
Segmental demyelination of a motor axon
Large onion bulbs - abundant connective tissue around thinly myelinated axons
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Nerve biopsy
Axonal degeneration
Investigations
Genetic testingThere are several routine genetic tests that can be requested
Myasthenia GravisAutoimmune weakness and fatigability of ocular, bulbar and striated muscle.
Neuromuscular junction
Myasthenia GravisAntibodies to acetylcholine receptor in 50% children
A firm diagnosis is based upon A characteristic history and physical examinationTwo positive diagnostic tests, preferably serological and electrodiagnostic.